The iPhone is the perfect metaphor for this ongoing ecological disaster

An iPhone is good for many things: staying connected with friends, finding your way around town, having the $4.

But it's also a perfect metaphor for one of the biggest environmental problems we're facing.

Think about how much you'd pay for an iPhone. A couple hundred bucks, right?

Now imagine it's missing one part. You'd probably take it if it were free, but you wouldn't want to pay for it. And if two parts are missing you'd be looking for a way to $4 as quickly as possible.

That's how we should be thinking about species extinction, Columbia University ecologist $4 said during at a World Science Festival panel on June 3. The rate of extinction has accelerated so much in recent years that $4 that as many as half of all living species could be gone by the end of the century - largely due to human activity.

It's hard to care about the loss of a bird or snake you'll never see living on the other side of the world.

But the animals, plants, and microbes we share the planet with are like $4 iPhone parts, said Naeem. They're each a critical part of the Earth's web of interconnected ecosystems. If we lose too many of these species, the planet will stop working the way we want it to - and unlike our iPhone, we can't upgrade Earth to the newest model.